If someone is underemployed full-time, they usually work full-time hours but worked less than 35 this month due to economic reasons (see Reason worked less than 35 hours [ABSENCEC]).

If someone is underemployed part-time, they usually work less than 35 hours and are willing and available to work more hours (see Whether part-time and looking for and available to work more hours [LAMHFUTC]).

Underemployment is only measured in the 'quarterly' labour force survey months: February, May, August and November (the second month of each financial year quarter).